This is a Conference grant of the Third International Conference on Lymphocyte Activation and Immune Regulation to be held at Newport Beach, California on February 16-18, 1990. The conference will last for two and a half day and comprised of 8 scientific sessions and one poster session. The main theme of this conference is the Development Biology of Lymphocytes. The topics to be discussed include phylogeny of lymphocytes, developmental biology of T cells, induction of tolerance, developmental biology of B cells and developmental biology of immunoglobulins. A special keynote lecture on developmental biology is slated. Several young investigators have been included in the list of speakers. Each invited lecture will be of 30 minutes followed by 10 minutes discussion. A poster session consisting of 20 selected free papers is slated for February 16th evening. The poster viewing will be followed by an hour of free discussion. A proceeding will be published within 6 months of the conference.